The present invention relates to a sealing material comprising a fluorine-based elastomer, particularly an elastomer sealing material used for semiconductor production and semiconductor delivery apparatus, which are required to have plasma resistance, heat resistance and chemical resistance.
Various plasma treatments, such as CVD (Chemical Vapor Deposition), etching or ashing, utilizing various plasma gases such as fluorocarbon-based gas plasma and oxygen plasma are conducted in the manufacture steps of semiconductor elements and liquid crystal panels, are employed. In a treatment apparatus using plasma, it is necessary to maintain the inside of a reactor in vacuo. For this purpose, elastomeric sealing materials are used for sealing various connecting sections or movable sections, such as chambers and gate valves.
Those elastomer sealing materials are required to have not only sealing properties but also plasma resistance and heat resistance capable of withstanding severe plasma processing conditions, and also have a property such that the materials do not generate particles which may contaminate semiconductors. Fluorine-based elastomers and silicone-based elastomers have conventionally been used as materials of the elastomer sealing materials that can meet those requirements.
Examples of the fluorine-based elastomers include perfluoro elastomers and fluorocarbon rubbers. Those have excellent resistance to fluorocarbon-based gas plasma but show large weight loss to oxygen plasma. On the other hand, examples of the silicone-based elastomers include silicone rubbers and fluorosilicone rubbers. Those rubbers have the characteristic that those have excellent resistance to oxygen plasma but show large weight loss to fluorocarbon-based gas plasma. Accordingly, it is the present status that a sealing material is chosen and used depending on the type of plasma. In many cases, fluorine-based elastomer sealing materials are used in plasma etching apparatus using mainly a fluorocarbon-based gas, and silicone-based elastomer sealing materials are used in plasma ashing apparatus using mainly oxygen.
In addition, there is a case where a quartz-made chamber or inspection window is used in a plasma-emitting section of a semiconductor production apparatus. When a silicone-based elastomer sealing material is used in such a section, the quartz and the sealing material are firmly adhered to each other, resulting in various problems. For example, even when it is intended to open the chamber during the maintenance, the sealing material is adhered to a flange and broken, and the sealing material is obliged to be exchanged, the matter of which is not supposed originally. Further, in the case where it is intended to open the inspection window, the sealing material causes adhesion so that quartz constituting a window material may possibly be broken. Moreover, during exchanging the sealing material, the sealing material is hardly peeled off, resulting in spending time and effort on the exchange operation. Thus, while the silicone-based elastomer sealing material is suitable in the section where the resistance to oxygen plasma is required, it becomes unsuitable in the section where quartz is used because it causes adhesion.
On the other hand, the fluorine-based elastomer sealing material does not substantially involve adhesion to quartz, but has the problem on resistance to oxygen plasma.
In the semiconductor production process, microwave energies are often utilized. According to discharge utilizing microwave energies, it is possible to localize the energies in a discharge space without need of electrodes. Further, according to this method, since contamination of impurities as seen in sputtering or the like can be avoided, it has an advantage that high-density, uniform and clean plasma can be formed. Accordingly, microwaves are eagerly used in various semiconductor production apparatus including an ECR (Electron Cyclotron Resonance) plasma CVD apparatus, a reactive ion etching apparatus, an ECR plasma etching apparatus and a plasma etching apparatus.
In the above-described semiconductor production apparatuses, rubber-made O-rings are used as a sealing material of a vacuum chamber. The rubber-made O-rings are mainly composed of a fluorocarbon rubber, a silicone rubber or a perfluoro elastomer, each having excellent heat resistance. However, those rubber materials involve a problem that those absorb the microwaves and generate heat, resulting in degradation.
In general, it is known that an amount of heat generation of the material depends on sizes of a dielectric constant and a dielectric dissipation of the material and that the lower both of the dielectric constant and the dielectric dissipation, the lower the heat generation is. For this reason, the rubber materials used in the semiconductor production apparatus utilizing microwaves are required to have not only a lower dielectric constant but also a lower dielectric dissipation. However, the above-described conventional rubber materials for rubber-made O-rings have high dielectric constant and dielectric dissipation in a microwave band having a frequency of 2.45 GHz as generally used in semiconductor production apparatus, and therefore, those generate a large amount of heat and generally have short life.
Of other rubber materials, EPDM (ethylene-propylene-diene terpolymer) has both low dielectric constant and low dielectric dissipation and also shows small amount of heat generation by microwaves. However, it involves a problem that the material has poor heat resistance.
In the light of the above, it is the present status that optimum rubber materials for apparatus utilizing microwaves have not been found yet.
Under such circumstances, the present invention has been made.
Accordingly, an object of the present invention to provide an elastomer sealing material having low dielectric constant and low dielectric dissipation, which is satisfactory with both of resistance to oxygen plasma and non-adhesion to quartz, and which can be applied to apparatus utilizing microwaves.
As a result of extensive and intensive investigations to overcome the above problems, it has been found that it is effective to improve resistance to oxygen plasma of a fluorine-based elastomer sealing material that is difficult to cause adhesion to quartz in a plasma-emitting section. The present invention has been completed based on this finding.
According to the present invention, a plasma-resistant fluorine-based elastomer sealing material is provided, which comprises a fluorine-based elastomer having a divalent perfluoropolyether or divalent perfluoroalkylene structure in the main chain thereof and having two or more hydrosilyl groups and addition-reactive alkenyl groups in the terminals or side chains thereof, and a polymer having two or more hydrosilyl groups in the molecule and being capable of addition reacting with the alkenyl groups, the fluorine-based elastomer being crosslinked with the polymer.
In a preferred embodiment, the plasma-resistant fluorine-based elastomer sealing material has a dielectric constant of 2.5 or less and a dielectric dissipation of 0.01 or less in a microwave band of from 1 GHz to 30 GHz.